In general, this invention relates to hard disk drive technology; more particularly, it relates to a drive having an inner diameter ("I.D.") ramp loading system that employs multiple-function spacer structure.
An important issue that arises in designing a hard disk drive relates to head parking which involves placing a head stack assembly in an appropriate position while there is no power applied to the drive. Generally, some type of head parking is needed to avoid problems that result if a spinup operation is initiated while a head contacts any part of a disk surface that defines a data recording zone. In accordance with some designs, each recording surface has a landing zone at which the head for that recording surface is parked. In accordance with other designs, a ramp loading system is provided. Some ramp loading systems are categorized as outer diameter ("O.D.") systems and others as I.D. systems. With either an O.D. system or an I.D. system, the head-position control system that controls the angular position of the head stack assembly performs a parking operation to unload the heads before completion of spindown, and performs a loading operation immediately after at least substantial completion of spinup. With an O.D. system, the unloading occurs adjacent the O.D. With an I.D. system, the unloading occurs adjacent the I.D. and can involve multiple phases including a seek phase at full spin rate followed by an unloading phase starting at a reduced spin rate and completed when the spin motor stops spinning.
For additional background regarding prior art I.D. ramp loading systems, see U.S. Pat. No. 5,644,451 to Chan et al., U.S. Pat. No. 5,574,604 to Berg et al., and U.S. Pat. No. 5,701,219 to Shafe.
The teachings of the prior art regarding I.D. ramp loading systems leave unresolved various significant technical difficulties with respect to designing a practical system for a high capacity, high performance, high rpm disk drive. In such a drive employing multiple disks in a disk stack, a tight three-way merge tolerance is demanded not only between the disk stack and the head stack, but also between the head stack and the ramp stack, as well as the ramp stack and the disk stack. The z-height variance of a ramp stack itself has to be minimized, while all the ramps have to be precisely machined to a sophisticated ramp profile, made from a thermally stable and wear resistant materials. The disk flutter at OD is a function of spin rate; thus, higher rpm drives have greater such disk flutter; this further stresses a tight head/disk merge for any OD load/unload system. This, coupled with dramatically increasing linear velocity at OD poses severe risk for loading/unloading a head onto a disk. In addition, a given range of the disk surface at OD has to be allocated to loading/unloading, which becomes a significant loss to the premium real estate for data recording.
Other technical difficulties arise in I.D. ramp loading systems designed in accordance with the prior art such as the teachings of the patents referred to above. There exists a significant need to overcoming such difficulties with a low cost approach appropriate for mass production of cost competitive drives. Lastly, it has not proven practical to add effective shrouding around the O.D. of the disk pack, and shrouding is critically important to minimizing motor power consumption, air turbulence and disk flutter in high performance disk drives with an extremely high track following requirement.